260 THE FORMS OF CELLS [ch. 



conditions of viscous or frictional restraint. A case which (as it 

 seems to me) is closely analogous to that of our foraminiferal 

 shells is described by Quincke*, who let a film of albumin or of 

 resin set and harden upon a surface of quicksilver, and found 

 that the little solid pelhcle had been 

 thrown into a pattern of symmetrical 

 folds. If the surface thus thrown into 

 folds be that of a cylinder, or any other 

 figure with one principal axis of sym- 

 metry, such as an ellipsoid or unduloid, 

 the direction of the folds will tend to 

 be related to the axis of symmetry, 

 ^^ and we might expect accordingly to 



find regular longitudinal, or regular transverse wrinkling. Now 

 as a matter of fact we almost invariably find in the Lagena 

 the former condition : that is to say, in our ellipsoid or unduloid 

 cell, the puckering takes the form of the vertical fluting on 

 a column, rather than that of the transverse pleating of an 

 accordion. And further, there is often a tendency for such 

 longitudinal flutings to be more or less localised at the end of the 

 ellipsoid, or in the region where the unduloid merges into its 

 spherical base. In this latter region we often meet with a regular 

 series of short longitudinal folds, as we do in the forms of Lagena 

 denominated L. semistrinta. All these various forms of surface 

 can be imitated, or rather can be precisely reproduced, by the art 

 of the glass-blower f. 



Furthermore, they remind one, in a striking way, of the 

 regular ribs or flutings in the film or sheath which splashes up to 

 envelop a ^smooth ball which has been dropped into a liquid, as 

 Mr W( r hington has so beauiifully shewn J. 



* Ueber piiysikalischen Eigenschaften dunner, fester Lamellen, S.B. Berlin. 

 Akad. 1888, pp. 789, 790. 



t Certain palaeontologists (e.g. Haeusler and Spandel) have maintained that 

 in each family or genus the plain smooth-shelled forms are the primitive and ancient 

 ones, and that the ribbed and otherwise ornamented shells make their appearance 

 at later dates in the course of a definite evolution (cf. Rhumbler, Foramini/eren 

 der Pla:'kton-Exi:)edition, 1911, i, p. 21). If this were true it would be of funda- 

 mental importance : but this book of mine would not deserve to be written. 



X A Study of Splashes, p. 116. 



